Electrostatic precipitator



y 0, 1969 D. D. MULLIN 3,444,667

ELECTROSTATIC PRECIPITATOR Filed March 1, 1968 Sheet INVENTOR.

DOYLE D. MULLIN A Hamil May 20, 1969 o. D. MULLIN ELECTROSTATIC PRECIPITATOR Sheet 2 01'2 Filed March 1. 1968 FIG 2 IN VENTOR.

- AHornay United States Patent 0 T 3,444,667 ELECTROSTATIC PRECIPITATOR Doyle D. Mullin, Minneapolis, Minn., assignor to Litton Systems, Inc., Beverly Hills, Calif., a corporation of Maryland Filed Mar. 1, 1968, Ser. No. 709,562 Int. Cl. 1303c 3/53, 3/40 US. Cl. 55-113 18 Claims ABSTRACT OF THE DISCLOSURE An electrostatic precipitator of the well known type in which particle ladened air is first passed through an electric field where the particles receive an electric charge of one polarity and then passed through another electric field where the charged particles are attracted to an electrode having the opposite polarity. The attracting or collector electrode is of the type which comprises a rotatable disk over which a film of liquid is caused to flow outwardly from the center thereof. The charged particles are electrically precipitated into the moving film of collector liquid and are thereby collected. The electrostatic precipitator has upper and lower casing sections with the upper casing section housing an air inlet nozzle and a rotatable collector disk and the lower casing section housing a variety of parts, including an exhaust chamber and an exhaust blower. Valve means for controlling the flow of air from the upper casing section to the exhaust chamber in the lower casing section is provided between the casing sections. The upper casing section is angularly moveable relative to the lower casing section and the valve means is controlled by this angular movement to vary the flow rate of the air which is drawn in through the inlet nozzle and passes over the rotatable collector disk.

BACKGROUND OF THE INVENTION This invention relates to improved apparatus for electrostatically precipitating particles from a particle ladened air or gas stream into a continuously flowing liquid.

One use for electrostatic precipitators of the type disclosed herein is for collecting samples of particles in the atmosphere which particles are subsequently analyzed for scientific purposes. When so used, the machine is in effect a scientific instrument and as such must have various controls which permit the flexible operation of the instrument so that desired objects of a variety of projects for which the instrument is used may be achieved. One such control relates to the control of the rate of air flowing through the precipitator. Although prior art electrostatic precipiators have been equipped with air fiow controls, the air flow control of the present invention is unique and has several advantages by reason of its being integrated into the basic design of an electrostatic precipitator.

SUMMARY OF THE INVENTION In the basic design of the electrostatic precipitator embodying the present invention there are separate and distinct upper and lower casings or casing sections. The upper casing section houses an inlet nozzle and a rotatable collector disk, and the lower casing section houses a variety of supporting equipment such as an exhaust chamber, motors, pumps, a blower, an electric power supply unit, liquid containers and an instrument and control panel.

The upper casing is of a generally cylindrical shape and the lower casing is of a generally rectangular box shape. The upper casing is made angularly moveable relative to the lower casing. The floor of the upper casing is provided with openings or air passages which cooperate with similar openings in the cover of the lower casing. When the upper casing is moved by an operator to various 3,444,667 Patented May 20, 1969 angular positions relative to the lower casing, the air flow rate is varied by reason of the upper and lower air passages being changed to varying degrees of overlapping from a fully open position to a fully closed position.

A main advantage of the invention is that it provides an air flow control for electrostatic precipitators which is integrated into the basic design of the machine and, hence, does not require auxiliary parts such as electric motor speed controls, a pivotally mounted damper or auxiliary housing sections such as an air duct in which a damper is mounted.

A main object of the invention is to provide a new and improved electrostatic precipitator and, more particularly, such a precipitator having new and improved air flow control means.

Another object is to provide a new and improved electrostatic precipitator having novel air flow control means integrated into the basic design of the precipitator. A related object is to provide air flow control means which does not include any major components, such as a damper or a variable speed blower motor, apart from structure which would have to be present anyway in an electrostatic precipitator not equipped with air flow control means.

Another object of the invention is to provide a new and improved electrostatic precipitator which is economical to manufacture and which provides efficient, trouble-free operation.

Other objects and advantages of the invention will become apparent from the following specification, drawings and appended claims.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of an electrostatic precipitator which embodies the invention;

FIG. 2 is a fragmentary elevational sectional view of the electrostatic precipitator shown in FIG. 1 taken on lines 22 of FIG. 1 and 22 of FIG. 4;

FIG. 3 is a perspective view showing the inside of the base section of the electrostatic precipitator with the cover for the base section removed; and

FIG. 4 is a sectional view taken on line 4-4 of FIG. 2.

Referring to the drawings, FIG. 1 shows a perspective view of an electrostatic precipitator embodying the invention which has a casing comprising two main sections which are a collector disk section 10 and a base section 12. Disk and base sections 10 and 12 may be made of a metal, such as aluminum, or from some other suitable material.

Base section 12 has a generally rectangular box shape and has a shelf section for holding two liquid containers 13 and 14 and an instrument and control panel 15. Container 13 is for holding a supply of collector liquid and container 14 is for holding a particle laden liquid containing sample aerosol particles collected in the course of the operation of the machine.

Instrument and control panel 15 comprises an air flow meter 16, a valve 17, a voltage indicator light 18, a sampling button 19, and a start button 20. These controls will be referred to further on in connection with a descrip tion of parts of the machine to which they relate.

Base casing section 12 has a rectangularly shaped cover 21 upon which disk casing section 10 is supported and with respect to which disk section 10 has limited angular movement, as will be explained.

'Disk casing section 10 is generally cylindrically shaped, and as may be noted in FIG. 2, is formed with two spaced apart floor and roof sections 22 and 24 and a cylindrically shaped wall section 26. Disk casing section 10 is symmetrical with respect to a vertically extending reference line and axis 28 which, for convenience of description, is referred to frequently herein. Roof section 24 has a central circular opening and a generally frustoconically shaped aerosol inlet member 32 which is one part of an inlet nozzle assembly, is attached to roof section 24 in surrounding relation to the circular opening '30. Inlet member 32 has an annular flange 34 at the lower end thereof which facilitates its attachment to the top of disk section 10. An annularly shaped insulator member 36, made of insulating material, is attached to the underside of roof section 24 and an annularly shaped high voltage plate or electrode 38 is attached to the lower end of the insulator member 36. The inlet nozzle assembly is completed by a frustoconically shaped nozzle member 40 having an annular flange 41 for attachment to the upper side of the electrode 38. The nozzle members 32 and 40 and the insulator 36 comprise a downwardly converging nozzle assembly and these parts are formed to provide a composite, downwardly converging, frustoconical inner surface for the nozzle assembly.

Annular plate 38 is an electrode which receives an electrostatic charge and a ring of needles 42 are attached to the lower side of plate 38 with the needles being symmetrically arranged in surrounding relation to the nozzle opening. The ring of needles 42 emits a corona sheath and particles in the air or gas stream passing through this corona sheath are electrically charged.

The floor 22 of disk casing section 10 has a cylindrically shaped circular recess, or downwardly protruding portion 43, which is symmetrically formed with respect to the main axis 28. This recess has a subfloor '44 and a cylindrically shaped wall 45. As can be best seen in FIG. 4, Subfioor 44 has a central opening 46 (with respect to axis 28) and radially spaced therefrom are a plurality of symmetrically arranged air passage openings which comprise a set of four relatively large openings 48 and a set of four relatively small openings 49. Subfioor 44 also has two are shaped slots 51 spaced radially outwardly from the large air passages 48 and symmetrically arranged relative to axis 28. Each slot has a circular opening 52 at one end thereof and the subtended angle for each slot is on the order of 52. The cover 21 of base section 12 has a collar 53 attached thereto which is symmetrical with respect to axis 28. C01- lar 53 has a cylindrically shaped, vertically standing wall 54 and an annularly shaped flange 55 to facilitate attachment of the collar to the cover 21. The inside diameter of collar 53 is slightly larger than the outside diameter of the downwardly protruding portion 43 of disk casing section 12 and the height of collar wall 54 is somewhat less than the height of wall of protruding portion 43-.

In the enclosure defined by collar 53, the base section cover 21 has a central opening 146, and air passages 148 and 149, which are illustrated (see FIGS. 2 and 3) as being exactly identical with respect to size and arrangement to the corresponding openings in the subfloor 44 of protruding portion 43. A circularly shaped gasket 57 made of a suitable material such as silicon sponge rubber and having the same diameter as the inside diameter of collar 53 is laid or disposed in the enclosure defined by the collar 53. Gasket 57 has a plurality of openings which are identical to the cover openings 146, 148 and 149 and the gasket is installed so that the openings thereof register or are in alignment with the cover openings. Two screws 58 are partially screwed into the base cover 21 on diametrically opposite sides of the axis 28 a radial distance, in each case, equal to the radius of each of the arc shaped slots 51. The head diameters of the screws 58 are slightly less than the diameters of slot holes 52. When the casing section 10 is originally placed or mounted on the casing section 12, the slot holes 52 register with the heads of screws 58 so as to allow the protruding section 43 of the casing section 10 to be received in the enclosure defined by cover collar 53 and in abutting engagement with the gasket 57. When casing section 10 is in its installed position the heads of screws 58 are slightly above the surface of subfloor 44. Slots 51 are of a lesser width than the diameters of the heads of screws 58 so that the screw heads will function to prevent casing section 10 from being lifted from the base section 12 after casing section 10 is moved angularly so that slot openings 52 are moved away from the screws 58. Screws 58 also have the function, along with cover collar '53, to retain casing section 10 in a central position relative to axis 28.

Referring to FIG. 3, base section 12 contains an exhaust chamber 60 which is defined by four vertically extending walls 61 which are spaced apart so that the cover openings 146, 148 and 149 are between these walls. Walls 61 are of a height such that the tops thereof are engaged by cover 21 in fiuid tight relation. A gasket (not shown) may be disposed between the tops of the walls 61 and the cover 21 if desired.

Referring to FIGS. 2 and 3, an elongated bracket 63 extends between and is attached to two opposite sidewalls 61. Bracket 63 has a bearing '64 attached thereto which is coaxial with respect to the axis 28. A shaft 65 is journalled in bearing 64 which has a bevel gear 66 attached to the lower end thereof and a toothed coupling 67 attached to the upper end thereof. Shaft 65 extends through the central openings in cover 21, gasket 57 and subfloor 44 so that the top of coupling 67 is disposed between the subfloor 44 and the floor 22 of dis-k casing section 10.

Beneath bracket 63 is a horizontally extending shaft 69 which extends between two opposite sidewalls 61 and is journalled in those walls. Shaft 69 is driven by a motor 70 which is mounted on one of the sidewalls 61 and shaft 69 functions to drive two peristaltic pumps 71 and 72 mounted on a wall 61 on the opposite side of the exhaust chamber from the motor 70. A bevel gear 73 is attached to shaft 69 and engages bevel gear 66 in driving relation to effect the rotation of coupling '67 by motor 70.

Referring to the internal construction of the disk casing section 10 (see FIG. 2), an elongated bracket 75 extends diametrically across the recessed floor portion and is attached at opposite sides thereof to the floor 22. A bearing or guide 76 is mounted centrally of the bracket 75 in alignment with the axis 28. Disposed in disk section 10 is a rotatable collector plate or disk 80 which has a generally flat upper surface 81 in spaced relation to the electrode plate 38 and the ring of needles 42. Disk 80 is mounted on a circularly shaped support member 82 having a shank portion '83 depending therefrom which is rotatably journalled in the bearing 76. Shank portion 83 has a central bore into which is press fitted a shaft 84. Shaft 84 has a toothed coupling 85 attached to the lower end thereof which is identical to toothed coupling 67 which it engages in rotatable driving relation. Disk 80 is thus driven by motor 70 through the drive connections described. The spacing between disk 80 and the electrode plate 38 may be in the range of between about one-half to one and one-fourth inches, but this dimension has to do with design considerations which are not material to the present invention.

Collector disk 80 has an annularly shaped, recessed trough 86 extending around the periphery thereof for a purpose to be explained further on herein. Disk 80 is rotatable relative to the disk casing section 10 and is vertically supported therein by three circumferentially spaced rollers 88 which are spaced radially inwardly from the disk trough 86. Three brackets 89 are provided for supporting rollers 88 for rotation about horizontal axes which are attached to the floor 22 of the disk casing section 10. Means (not shown) may be provided to facilitate the vertical adjustment of each roller 88 relative to its bracket 89 to allow for the precise spacing of the disk 80 relative to the electrode plate 38.

It is mentioned above that the motor 70 (see FIG. 3) which drives the disk 80 and the pumps 71 and 72 is attached to one of the walls 61 of the exhaust chamber 60. Mounted on adjacent walls 61 are another motor 90 and a blower 91 which cooperate and function to exhaust air from the exhaust chamber 60. A shaft 92 for driving the blower 91 extends from the motor 90 to the blower. Blower 91 functions to draw an air or gas into the inlet nozzle to the exhaust chamber 60 and return the air to the atmosphere, through an air duct 93 which extends from the blower to the exterior of the base section 12.

Also mounted in base section 12 is a high voltage power supply 94.

In the disk casing section 10 there is disposed a collector liquid conduit 95 whch terminates immediately above the center of disk 80 and extends vertically therefrom. Conduit 95 also extends radially outwardly through the insulator 36 to the casing wall 26 and then downwardly.

An aspirating probe 96 is mounted in one of the roller brackets 89 so that the probe is disposed in disk trough 86 in tangential spaced relation to the sides and bottom of the trough. The probe 96 is formed and mounted so that it can be swung away from the top of disk 80 so as to provide sufiicient clearance to allow the disk to be lifted up and readily removed from its installed position. A conduit 98 is connected to the probe 96 and extends downwardly therefrom in grouped relation to the conduit 95.

An insulated electrical connector 99 is electrically connected to the electrode plate 38 and also extends downwardly adjacent the casing wall 26.

Small holes are provided in the floor 22 of casing section 10 through which the two conduits 95 and 98 and the conductor 99 extend to the outside of the casing section 10. Ring shaped rubber grommets or the like are provided to seal these three holes to limit or prevent air from entering the casing section 10 which has a subatmospheric pressure during operation of the machine.

An opening 100 is provided in the cover 21 of base section 12 through which the two conduits 95 and 98 and the conductor 99 enter into the interior of base section 12.

The peristaltic pumps 71 and 72 are of the positive displacement type. Collector liquid conduit 95, after entering the base section 12 through the opening 100, extends to the valve 16, to the pump 71 and to the collector liquid container 13. The aspirating probe conduit 98 extends through the opening 100 to the pump 72 and then to the container 14 which receives the particle ladened collector liquid. Conductor 99 extends from the hole 100 to the electrical power supply unit 94.

In the operation of the machine the start button is actuated and this has the effect of starting the two motors 70 and 90. Operation of the motor 70 causes rotation of the collector disk 80 and the operation of the two pumps 71 and 72. Operation of the motor 90 operates the blower 91 to cause the air to fiow into the inlet nozzle, around the disk 80, through the openings 48 and 49 in the subfioor 44 of the casing section 10 and the openings 148 and 149 in the casing cover 21.

After button 20 is actuated to start the motors 70 and 90, collector liquid in container 13 may be delivered to the top of the rotating disk 80 by turning the valve 17, which is of a modulating type, to an open position. Container 13 may be equipped with a liquid flow meter and the collector liquid may thus be caused to be delivered to the disk 80 at a desired rate of flow by adjusting the valve as dictated by the reading of the liquid flow meter. The scale range of the liquid flow meter may be on the order of from 0 to about milliliters per minute, for example.

In conjunction with the delivery of collector liquid to the disk 80, the aspirating probe 96 withdraws the collector liquid which flows into the disk trough 86 from the trough and delivers it through the conduit 98 to the container 14, the liquid being drawn through the conduit 98 by reason of the suction or aspirating effect created by the pump 72.

In the operation of the machine, air is caused to be drawn through the machine and the collector liquid is delivered from container 13 to the disk 80 and returned to the container 14 but no particles are collected from the air passing through the machine until an electric potential is provided between the electrode plate and the disk 80. This electric potential is supplied by actuating the sampling button 19 which has the effect of actuating the power supply unit to establish an electrostatic potential in the range of 15,000 volts across electrode plate 38 and the disk 80. Means (not shown) are provided for grounding the disk to complete the electrical circuit. The electric potential maintained between the plate 38 and the disk 80 has the effect of causing (1) a corona to be emitted from the ring of needles 42 which ionizes the air and thereby imparts an electrical charge to the particles carried by the air, and (2) creates an electrical force which precipitates the charged particles onto the radially outwardly flowing liquid film on the rotating collector disk 80. Particles collected on or in the liquid film on the collector disk 80 float or are carried to the annular trough 86, which rotates by reason of being associated with the collector disk 80, and the particle ladened liquid is withdrawn from the trough by the suction effect of the aspirating probe 96.

It is essential in operating the machine to vary the fiow of air therethrough. As mentioned above, and as is obvious from the structure described, disk casing section 10 is angularly moveable about axis 28 relative to the base section 12. In one angular position of the casing section 10 the holes 48 and 49 in the subfioor 44 thereof may be in exact overlapping alignment with the corresponding holes 148 and 149 in the base cover 21 so that maximum sized openings are presented through which a maximum flow of air is obtained. Angular movement of the casing section 10 will cause a progressive reduction of the effective areas of the openings to the point where the openings are fully closed and there is no flow of air into the exhaust chamber 60.

The air flow meter 16 has conventional tubes or conduits (not shown) leading therefrom to the interior of the air outlet duct 93 for sensing the flow of air therethrough and this is indicated quantitatively by the meter 16. Meter 16 has an air flow scale with suitable units such as thousands of liters per minute indicated thereon. The turning of casing section 10 varies the air flow through the machine, as explained above, and an operator may thus select a desired air flow by simply adjusting the angular position of the casing section 10 in one direction or the other until the desired flow rate is indicated on the meter 16.

What is claimed is:

1. An electrostatic precipitator having a casing which comprises a base section and a collector disk section, said base section having a cover with a drive means opening and at least one air passage opening radially spaced from said drive means opening, said base section having an exhaust chamber in fluid communication with said air passage opening, said disk section having an inlet opening for admitting aerosol thereto, means for imparting electrical charges to particles of said aerosol, an oppositely chargeable rotatable collector disk to which said particles are electrostatically precipitated disposed in said disk section, means in said disk section for supplying a flow of collector liquid to said disk, means in said disk section for guiding said aerosol over said disk, said disk section having a floor with a central opening in alignment with said drive means opening and at least one air passage radially spaced from said central opening, drive means in said base section for driving said disk, means extending through said drive means opening and said central opening for connecting said drive means and said disk in driving relation, said disk section being angularly adjustable relative to said base section to move said air passage of said disk section into varying degrees of alignment with said air passage of said base section to vary the flow of air therethrough.

2. An electrostatic precipitator according to claim 1 wherein said base section cover and said disk section floor are abutting members with the Weight of said disk section being supported by said cover, one of said members having a circular protruding portion concentrically arranged relative to said drive means opening, the other of said members having a collar forming a circular enclosure for receiving said protruding portion, said collar being of slightly larger diameter and of lesser height than said protruding portion.

3. An electrostatic precipitator according to claim 2 wherein said collar is afiixed to said cover of said base section.

4. An electrostatic precipitator according to claim 1 wherein support and bearing means are provided in said disk section for providing vertical and lateral support for said collector disk.

5. An electrostatic precipitator according to claim 4 wherein said support and bearing means comprise a centrally located radial thrust bearing in alignment with said drive means opening and a plurality of rollers circumferentially arranged relative to said drive means opening, said rollers being mounted for rotational movement about horizontal axes.

6. An electrostatic precipitator according to claim 2 wherein one of said members includes a gasket made of rubber or a rubber-like material having a slightly smaller outside diameter than said circular enclosure and being disposed in said circular enclosure between said base and disk sections.

7. An electrostatic precipitator according to claim 6 wherein said gasket is attached to said base section cover and has openings which register with said openings in said cover.

8. An electrostatic precipitator according to claim -1 wherein said means extending through said drive means opening comprises a rotatable and vertically extending shaft having a coupling member at the upper end thereof within the confines of said disk section, said disk having a downwardly extending shaft with a coupling member at the lower end thereof which engages said first named coupling member in driving relation.

9. An electrostatic precipitator according to claim 1 including first conduit means for supplying a collector liquid from said base section to said disk section, second conduit means for drawing a particle ladened collector liquid from said disk section to said base section, and electrical conduit means extending from said base section to said disk section.

10. An electrostatic precipitator according to claim 9 wherein each of said conduit means extends through a small opening in said floor of said disk casing section and grommet means are provided between each of said conduit means and said floor to respectively seal said small openings.

11. An electrostatic precipitator having a casing including a base section having a cover provided with at least one air passage opening extending therethrough, said base section having an exhaust chamber in fluid communication with said air passage opening, said casing also including a collector disk section having an inlet opening for admitting aerosol thereto, a collector disk mounted in said disk section, said disk section having a floor with at least one air passage and being angularly adjustable relative to said base section to move said air passage of said disk section into varying degrees of alignment with said air passage of said base section to vary the amount of air flowing onto said collector disk.

12. An electrostatic precipitator according to claim 11 wherein said base section cover and said disk section floor are abutting members with the weight of said disk section being supported by said cover.

13. An electrostatic precipitator according to claim 12, wherein one of said members has a circular protruding portion concentrically arranged relative to said drive means opening and the other of said members has a collar forming a circular enclosure for receiving said protruding portion, said collar being of slightly larger diameter and of lesser height than said protruding portion.

14. An electrostatic precipitator'having a casing which comprises a base section and a collector disk section, said base section having a cover with a drive means opening and'at least one air passage opening radially spaced from said drive means opening, said base section having an exhaust chamber in fluid communication with said air passage opening, said disk section having an inlet opening for admitting aerosol thereto, a collector disk rotatably mounted in said disk section, said disk section having a floor with a central opening in alignment with said drive means opening and at least one air passage radially spaced from said central opening, drive means in said base section for driving said disk, means extending through said drive means opening and said central opening for connecting said drive means and said disk in driving relation, said disk section being angularly adjustable relative to said base section to move said air passage of said disk section into varying degrees of alignment with said air passage of said base section to vary the flow of air therethrough.

15. An electrostatic precipitator according to claim 14, wherein said base section cover and said disk section floor are abutting members with the weight of said disk section being supported by said cover.

16. An electrostatic precipitator according to claim 14 wherein support and bearing means are provided in said disk section for providing vertical and lateral support for said collector disk.

17. An electrostatic precipitator according to claim 16 wherein said support and bearing means comprise a centrally located radial thrust bearing in alignment with said drive means opening and a plurality of rollers circumferentially arranged relative to said drive means opening, said rollers being mounted for rotational movement about horizontal axes.

18. An electrostatic precipitator according to claim 14 wherein said means extending through said drive means opening comprises a rotatable and vertically extending shaft having a coupling member at the upper end thereof within the confines of said disk section, said disk having a downwardly extending shaft with a coupling member at the lower end thereof which engages said first named coupling member in driving relation.

References Cited UNITED STATES PATENTS 1,869,772 8/1932 Paterniti 55-114 1,917,310 7/1933 Lesage 55-417 X 2,064,587 12/ 1936 Carlstedt 55-417 X 2,336,625 12/1943 Milton 55-113 2,675,090 4/1954 Landgraf 55-122 2,868,322 1/1959 Stautfer 55-419 X 2,949,167 8/1960 Bergstedt 55-152 3,035,445 5/1962 Evans et al. 55-122 X 3,148,146 9/1964 Asnes et al 233-11 3,232,094 2/1966 Teschner 73-28 3,392,512 7/1968 Ziolko et a1. 55-400 3,401,503 9/1968 Bergstrom 55-155 X HARRY B. THORNTON, Primary Examiner. D. E. TALBERT, J r. Assistant Examiner.

U.S Cl. X.R. 55-118, 122, 128, 149, 152, 154, 417; 73-28 

